Dillip K. Pradhan

Effect of Mn substitution on electrical and magnetic properties of Bi0.9La0.1FeO3

Polycrystalline samples of Bi0.90La0.10(Fe1−xMnx)O3 (x=0, 0.05, 0.10, 0.15, and 0.20) were prepared using a novel mechanical activation followed by a conventional solid-state reaction technique. The formation of the desired materials was confirmed using x-ray diffraction. The electrical and magnetic properties of the materials were investigated at different Mn concentrations as a function of temperature. Both dielectric constant and loss tangent increased with the increase in Mn content in the system. The grain and grain boundary contributions have been estimated using impedance spectroscopy analysis. Both grain and grain boundary conductivity increased with a rise in temperature for all Mn concentrations. The value of activation energy for both grain and grain boundary is nearly the same, and decreased with an increase in Mn concentration. There is a systematic increase in the value of magnetization on increasing Mn concentration.

Relaxor characteristics of Pb(Fe2/3W1/3)O3 -BiFeO3 solid solution prepared by mechanosynthesis route

The polycrystalline nanosize (∼60nm) of (1−x)Pb(Fe2∕3W1∕3)O3–x(BiFeO3) solid solutions with a wide range of concentrations (0⩽x⩽0.20) were fabricated using a mechanical activation followed by a conventional solid-state reaction technique. The formation of single-phase material and better solubility of two phases [i.e., BiFeO3 (BFO) and Pb(Fe2∕3W1∕3)O3 (PFW)] were confirmed using an x-ray diffraction technique. Studies of frequency and temperature dependences of dielectric parameters of solid solutions have provided unique relaxor characteristics of PFW on substitution of a critical composition (i.e., 10%) of BFO in it. The loss tangent (tanδ) peaks of PFW are frequency dependent above room temperature. The sharp tanδ peaks of PFW diffuse on increasing BFO content in PFW–BFO solid solution. This exhibits the induction of relaxation properties in the nonrelaxor PFW material. An ac conductivity (σac) of solid solutions is very much dependent on the frequency and temperature. The nature of temperature depende...

Effect of Sr substitution on tunability and dielectric properties in Pb(Zr0.50Ti0.50)O3 thin films fabricated by chemical solution deposition

(Pb1¿xSrx)(Zr0.5Ti0.5)O3 ( x= 0 to 0.65) thin films were grown on Pt/TiO2/SiO2/Si substrates by chemical solution deposition. Films were crystallized in the single phase perovskite structure in the temperature range ( 550¿700°C). Dielectric constant and loss tangent at room temperature reduced as the percentage of Sr substitution increased at the A-site of this perovskite structure. The phase transition temperature (Tc) lowered with Sr-substitution and Tc below the room temperature was obtained for composition with Sr ¿ 40%. The room temperature tunability reduced with Sr substitution, however, the k-factor slightly improved.

Phase Transition and Dielectric Tunability of Chemical Solution Deposited (Pb 0.35 Sr 0.65 )(Zr 0.5 Ti 0.5 )O 3 Thin Films on Pt/ZrO 2 /SiO 2 /Si Substrates

(Pb 0.35 Sr 0.65 )(Zr 0.5 Ti 0.5 )O 3 thin films were grown on Pt/ZrO 2 /SiO 2 /Si substrates by chemical solution deposition. As-deposited (pyrolysed at 500°C) films were amorphous and single phase films were obtained at temperature as low as 550°C with a 30 nm SrTiO 3 seed layer. Dielectric constant and loss tangent at room temperature were 210 and 0.022, respectively at 100 kHz for the film annealed at 700°C. Frequency dispersion of the dielectric properties was low. The phase transition temperature (ferroelectric to paraelectric) was well below the room temperature and was around 220 K. The room temperature tunability and the k-factor at 500 kV/cm was around 45% and 16, respectively.